Method of electrically welding a capacitor electrode to the capacitor housing

ABSTRACT

A method of electrically connecting an electrode of a capacitor roll which is supported by a metal pin to the bottom of a capacitor housing. To this end, a metal strip which is connected to the electrode is clamped between the metal pin and the bottom, after which an electric current is fed through the pin, the strip and the bottom.

United States Patent 11 1 Bugel v METHOD OF ELECTRICALLY WELDING ACAPACITOR ELECTRODE TO THE CAPACITOR HOUSING Inventor: Roelof DirkBugel, Hattem,

Netherlands Assignee: U.S. Philips Corporation, New York,

Filed: Apr. 25, 1972 Appl. No.: 247,374

Foreign Application Priority Data l u l I l l l I l J [111 3,754,113[451 Aug. 21, 1973 [56] References Cited UNITED STATES PATENTS 3,174,0853/1965 Schroeder 29/570 3,555,370 1/1971 Bowling 37/230 PrimaryExaminer-E. A. Goldberg Attorney-Frank R. Trifari [57 ABSTRACT A methodof electrically connecting an electrode of a capacitor roll which issupported by a metal pin to the bottom of a capacitor housing. To thisend, a metal strip which is connected to the electrode is clampedbetween the metal pin and the bottom, after which an I electric currentis fed through the pin, the strip and the bottom.

4 Claims, 3 Drawing Figures 1 METHOD OF ELECTRICALLY WELDING A CAPACITORELECTRODE TO THE CAPACITOR HOUSING The invention relates to a method ofelectrically connecting an electrode of a capacitor roll which issupported by a metal pin to the inner side of a metal bottom portion ofa Capacitor housing.

According to a known method of the kind set forth, before the capacitorroll supported by a metal pin is inserted into. the empty housing, along metal strip, connected to the roll situated outside the capacitorhousing, is welded to thebottom portion by inserting a first weldingelectrode intov the housing and by clamping the strip between the bottomportion and said welding electrode by means of a second weldingelectrode which is pressed against the bottom portion from the outside.Subsequently, a current of sufficient intensity is fed through thebottom portion and the strip. After withdrawal of the welding electrodefrom the capacitor housing, the capacitor roll, held outside the housingand supported by the metal. pin, is slid into the housing where it isfixed in the usual manner.

One of the drawbacks of the described known method is that the alreadywelded, long metal strip is folded when the roll is inserted into thehousing, so that mechanical stresses are liable. to arise at the. weldarea, which may cause, deterioration or even facture of the weld. Afurther drawback is that the metal strip folded between the bottom ofthe, housing and the roll may give rise to short-circuits by penetrationof the end face of the roll. A further drawback yet is that the roll hasto be held outside the housing by suitable means during welding.

The invention has for its object to obviate the said drawbacks.

Tothis end, the invention is characterized in that the capacitor rollsupported by a metal pin is slid into the capacitorhousing so far that ametal strip connectedto the said electrode is clamped between the metalpin and the bottom portion, such a current being subsequently fedthrough the metal.pin,.the metal strip and the bottom portion, that themetalstrip iswelded to the bottom portion, after which the metal pin,with the capacitor roll is pulled away from the, bottomportionandisfixed in the capacitor housing.

So as to reduce. the risk that the metal pin is welded to themetalstrip, or in other wordsso as to attain a comparatively highcurrent density between the metal stripandthe metal'bottom portion and acomparatively low current density between the metal strip and the metalpin, in a special embodiment of .the methodaccording to the invention atleast one of the sides of the metal stripand the metal bottom portionfacingjeach" other are profiled such that the contact area of theprofilewith the metal strip is substantially smaller than the FIG. 3 isa sectional view through the capacitor housing bottom of a specialembodiment of an electrolytic capacitor according to the invention.

The electrolytic capacitor shown in FIGS. 1 and 2 comprises an aluminumcapacitor housing 1 which is open on one side and whose bottom 3 isprovided with an electric roll connection strip 5. Arranged in thecapacitor housing is an anode pin 7 made, for example, of aluminum,which is secured in a hard paper disc 9 and a rubber disc 11 and whichis provided with an electric connection strip 13. Arranged about theanode pin '1 is a roll 15 comprising, successively from the inside tothe outside, a formed aluminum anode foil, a

paper foil which is impregnated with a commonly used electrolyte, analuminum cathode foil, and a second impregnated paper foil. The anodepin 7 is at the same time used as the winding mandrel. So as to preventshort-circuits, the width of the paper foil is chosen to be larger thanthat of the aluminum foil. The portion 17 of the cathode foil extendsoutside the contour of the roll 15 and must be electrically connected tothe bottom 3 of the capacitor housing 1.

The portion 17 of the cathode foil (outer electrode) is clampedaccording to the invention between the anode pin 7 whichprojects outsidethe contour of the roll 15 and the bottom 3 of the capacitor housing 1.A first electrode 19 is pressed from the outside against the bottom 3and a second electrode 21 is pressed against a button-like end 23 of theanode pin 7. The electrode 19 is then slid over the connecting strip 5,whilst the electrode 21 is slid over the connecting strip 13. Theelectrodes 13"and 21 are subsequently connected to a current sourcewhich feeds a current through the bottom 3 of the capacitor housing,portion 17 of the cathode foil and the anode pin 7 of an intensity suchthat a reliable welded joint is obtained between portion 17 of thecathode foil and the bottom 3 of the capacitor housing 1. The electrodes19 and 21 are withdrawn after the current has been switched off. Theanode pin 7 with the roll 15 is then displaced with respect to thecapacitor housing 1 such that approximately the position shown in FIG. 2is reached. Next, a circumferential rill25 is pressed into the capacitorhousing 1 just below the hard' paper disc 9, after which the edge at theend of the housing 1': is spun over as is shown at 27 in F IG. 2. Thefinallocation of the discs 9 and 11 with respect to the capacitorhousing, and hence the location of anode pin'7 and roll 15, is thus laiddown.

In a special embodiment of the method according to the invention, thebottom 3 is provided with a spherical raisedportion29 from the inside ofthe capacitor housjoint is obtainedbetween the raised portion 29 and thestrip. Instead of being provided with a spherical raised portion 29,the-bottom 3 may also be provided with other suitable profiles such as,for example, rills. It is alternatively possible-to provide the side ofthe strip facing .the bottom 3 with a suitable profile such'as, forexample, small identations.

So as to reduce the contact resistance between the anode pin 7 and thestrip 17, the end face of the anode pin 7 facing the strip 17 can beroughened, for example, by grinding. Any aluminum oxide film presentwill thus be broken up so that an intimate metallic contact is obtainedbetween the anode pin 7 and the strip 17.

The portion 17 which is welded to the bottom 3 of the capacitor housingneed not necessarily be a continuation of the cathode foil, but may alsobe formed by a separate metal strip which is welded to the cathode foil.The separate connection between electrode and metal strip is thusavoided.

The method according to the invention can be successively applied forelectrolytic capacitors containing a liquid electrolyte as well as forelectrolytic capacitors having a semi-solid or solid electrolyte, andalso for non-electrolytic roll capacitors.

A method according to the invention is particularly suitable for bulkmanufacture because the multiple function of the anode pin, i.e.,winding mandrel, weldihg electrode and current conductor, constitutes areduction of the number of operations with respect to the known methods.

What is claimed is:

l. The method of structurally connecting an electrode of a capacitorroll to an inner side of a bottom portion of a capacitor housing, saidcapacitor roll being supported by a pin and said electrode connected toa strip member, said method comprising the steps of:

A. inserting the capacitor roll and pin into the capacitor housingsufficiently far enough to clamp .said strip member between the pin andthe bottom portion of said capacitor housing;

B. feeding current through the pin so as to weld the strip member tosaid bottom portion;

C. detaching the pin from said strip member; and

D. fixing the pin within the housing in the detached position.

2. The method of claim 1, wherein a high current density is achieved atthe weld between said strip member and said bottom portion by providingsaid bottom portion and strip member with a contact area that isconsiderably smaller than that common to the pin and strip member.

3. The method of claim 2, wherein said smaller contact area is providedby forming a raised portion in the housing bottom portion adjacent saidstrip member.

4. The method of claim 1, wherein said capacitor roll is provided forinsertion into said housing by first forming-said roll about said pinfrom successive layers of aluminum anode foil, a first paper foilimpregnated with an electrolyte, an aluminum cathode foil, and a secondimpregnated paper foil, said anode foil contacting said pin and aportion of the cathode foil serving as said strip member for attachmentto said housing.

1. The method of structurally connecting an electrode of a capacitorroll to an inner side of a bottom portion of a capacitor housing, saidcapacitor roll being supported by a pin and said electrode connected toa strip member, said method comprising the steps of: A. inserting thecapacitor roll and pin into the capacitor housing sufficiently farenough to clamp said strip member between the pin and the bottom portionof said capacitor housing; B. feeding current through the pin so as toweld the strip member to said bottom portion; C. detaching the pin fromsaid strip member; and D. fixing the pin within the housing in thedetached position.
 2. The method of claim 1, wherein a high currentdensity is achieved at the weld between said strip member and saidbottom portion by providing said bottom portion and strip member with acontact area that is considerably smaller than that common to the pinand strip member.
 3. The method of claim 2, wherein said smaller contactarea is provided by forming a raised portion in the housing bottomportion adjacent said strip member.
 4. The method of claim 1, whereinsaid capacitor roll is provided for insertion into said housing by firstforming said roll about said pin from successive layers of aluminumanode foil, a first paper foil impregnated with an electrolyte, analuminum cathode foil, and a second impregnated paper foil, said anodefoil contacting said pin and a portion of the cathode foil serving assaid strip member for attachment to said housing.